JPS61116081A - Pump control device - Google Patents

Abstract

PURPOSE:To make it possible to prevent cavitation on the suction side of a pump from the second one downward and steadily feed a target flow rate in pressurized state by controlling the pressure of a pump mounted downstream for proper suction pressure corresponding to the discharge pressure of a pump mounted upstream and a flow rate through piping. CONSTITUTION:Plural pumps 4, 5 are directly coupled with piping 10. The operation of the most upstream pump 4 is controlled on the set value of a target flow rate SV1 and the detected value of a flow rate PV1. The downstream pump 5 is controlled by an adjusting device for the number of revolution 12 in comparison of the detected value of speed PV4 read on a speed detector 3 with the set value of speed SV4. The set value of speed SV4 is determined by calculating the detected value of pressure PV3 and the set value of pressure SV3 on the suction side of the pump 5, and is output by a pressure adjusting device 15. In addition, the set value of pressure SV3 is determined by calculating the detected value of pressure and that of flow rate PV1 on the discharge side of the upstream pump 4 by means of an arithmetic and logic unit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pump control device for a fluid transfer system having a plurality of pumps connected in series through conduits.

(Technical Background of the Invention and Problems Thereof) In a water supply system in which pumps are spaced several stories apart, there is a method in which a buffer tank is provided in the middle of the system to control the pumps at uniform speeds.

FIG. 2 is a system diagram showing the configuration of this type of control device together with the objects to which it is applied. In FIG. 2, when sewage, etc. accumulated in the water pump well 9 is to be pumped to a distant place, the water pump 4 is installed near the water pump well 9, and the water pump 5 is installed at a position several minutes away from the water pump well 9. A buffer tank 11 is provided on the way, and the water pump 4 pumps the water from the water pump well 9 to the buffer tank 11, and the water pump 5 pumps the water from the buffer tank 11 to a further distance via a pipe 10.

Here, the flow rate m is adjusted based on the deviation between the flow rate setting m5v1 obtained by setting the water supply target flow rate to control the water supply pump 4 and the flow rate detection value Pv1 of the flow rate detector 6 provided in the pipe line 10. Total 1 outputs speed setting 1iIS■2, while this speed setting value SV2 and speed detection value P of speed detector 3
(2) The rotation speed controller 2 adjusts the rotation speed of the water pump 4 so that the deviation from the water pump 4 becomes zero.

In order to force-feed the water pump 5 with the same amount of water as the water pump 4, the speed setting value SV2 output from the flow m controller 1 is set to the telemeter 7 on the water pump 4 side and the telemeter 7 on the water pump 5 side. 8, water pump 5
In addition to the rotation speed controller 2 on the side, by adding the speed detection value Pv3 of the speed detector of the water pump 5 to the rotation speed controller 2, the water pump 5 is adjusted so that the deviation becomes zero.
The rotation speed is adjusted.

Therefore, the water pumps 4 and 5 are controlled at the same speed, but even if there is a slight difference in the amount of water sent between the two, the water level in the buff 7 tank 11 will go up or down. In addition to requiring an interlock circuit to stop the pump 5, maintenance of the buffer 7 tank 11 was essential.

However, the conventional pump control device shown in FIG. 2 has the drawback that construction of the buff 7 tank 11, installation and maintenance of the interlock circuit require a large amount of cost.

In order to improve this drawback, the buffer tank 11 is removed and the water pumps 4 and 5 are directly connected by a pipe 10,
A method of controlling the water pumps 4 and 5 at the same speed may also be considered.

However, in this case, cavitation occurs during water supply because the water supply pressure decreases due to head loss due to topographical differences between the two pumps, differences in pipe resistance due to piping structure and aging, etc. Also, there was a disadvantage that the pump was damaged.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks.
The object of the present invention is to provide a pump control device that can stably pump a target flow rate without damaging pipes and water pumps, and can significantly reduce device costs including construction costs.

[Summary of the invention]

In order to achieve this object, the present invention provides a pump control device for a fluid transfer system having a plurality of pumps connected in series through a pipe, including a flow rate detector for detecting the flow rate of the pipe, and a first control system that controls the upstream pump so that the flow rate of the upstream pump is equal to the set layer; a first pressure detector that detects the discharge side pressure of the upstream pump;
a calculation means for calculating the suction side pressure of the adjacent downstream pump based on the detected values of the first pressure detector and the 1irJ flow rate detector; and a second calculation means for detecting the suction side pressure of the downstream pump. The present invention is characterized in that it includes a pressure detector, and a second control system that controls the pump on the downstream side so that the suction side pressure becomes equal to the suction side pressure calculated by the calculation means.

[Embodiments of the invention]

FIG. 1 is a system diagram showing one embodiment of the present invention, and the same reference numerals as in FIG. 2 indicate elements that are the same or have the same effect.

In this FIG. 1, the water pumps 4 and 5 are
is connected in series with the flow rate detector 6 provided in the conduit 10, its flow rate detection @PV1, and a flow rate controller 1 that obtains a speed set value S2 corresponding to the deviation of the flow rate set value S1.
, a speed detector 3 that detects the rotational speed of the water pump 4, and a rotation speed that adjusts the water pump 4 so that the deviation between the speed setting isv and the speed detection value P2 of the speed detector 3 becomes zero. Flow ωii with controller 2! It constitutes the I'#J system.

Further, a pressure detector 12 for detecting the water supply pressure is provided on the outlet side of the water supply pump 4, and the pressure detection value of this pressure detector 12 and the flow rate detector of the flow rate detector 6 are connected to the telemeters 7 and 8. The water is then sent to the numbing device 13 provided on the water pump 5 side.

The calculator 13 calculates the inlet pressure of the water pump 5 based on the detected pressure value and the detected flow rate input thereto, and outputs a pressure set value Sv3.

Next, a pressure detector 1 installed on the input side of the water pump 5
4. Pressure adjustment practice 15 to obtain a speed setting value S■4 corresponding to the difference between the pressure detection value P■3 of the pressure detector 14 and the pressure setting value SV3 of the calculator 13. Detecting the rotational speed of the water pump 4. speed detector 3 and speed setting value S■4
A pressure control system is constituted by a rotation speed controller 2 that adjusts the water pump 5 so that the deviation between the speed value P and the speed detection value P4 of the speed detector 3 becomes zero.

The operation of this embodiment configured as described above will be explained below.

First, a flow rate adjustment system including a flow rate controller 1 and a rotation speed controller 2 is used to make the pumping flow rate equal to the set point.
Water pump 4 is controlled.

At this time, when the flow rate detection value of the flow rate detector 6 and the pressure detection value of the pressure detector 12 are added to the calculator 13, the inlet side pressure of the water pump 5 is calculated. This will be explained in more detail.

Since the water pump 4 and the water pump 5 are connected by the pipe 10, Bernoulli's theorem can be applied to the discharge side of the water pump 4 and the suction side of the water pump 5, respectively.
The following relationship holds true.

□ρv +g+ρgh=a・・・・・・・・・(1)
However, ρ: original fluid density V: flow rate p, pressure g: acceleration of gravity h: water head a: constant.

Therefore, the following relationship holds between the discharge side of the water pump 4 and the suction side of the water pump 5.

however ■1: Discharge side flow rate of water pump 4 v2 Suction side flow rate of the second water pump 5 p1; Discharge side pressure of water pump 4 ρ2: Suction side pressure of water pump 5 h1: Water head on the discharge side of the water pump 4 h: Water head on the suction side of the water pump 5 It is.

Further, the above equation (2) can be modified as follows.

+9g (h - h2) + P1 = P, -ρg (h2 - hl) -P h k v 1 ......
(3) However: This is the pipe line head loss.

In this way, the pressure on the suction side of the water pump 5 can be calculated from the pressure on the discharge side of the water pump 4 and the flow rate, so in this embodiment, the flow rate detection value, which is a substitute for the flow rate, and the pressure detection value are sent to the calculator 13. In addition, the pressure set value SV3 is calculated here.

Next, the water pump 4 is controlled by the flow rate control system including the pressure regulator 15 and the rotation speed regulator 2 so that the pressure on the suction side of the water pump 5 becomes the set pressure calculated by the calculator 13.

Thereby, the suction side pressure of the water pump 5 is appropriately controlled, and the target flow rate can be stably supplied while suppressing the occurrence of cavitation.

In the above embodiment, control of two water pumps was explained, but three or more water pumps may be used.

Even in a system where the water pump is used, the pressure on the suction side of the downstream water pump can be calculated based on the pressure on the discharge side of the upstream water pump and the flow rate of the pipeline, so the same control as described above is possible.

Furthermore, although the above embodiments have been described with respect to a water supply system, the present invention can be applied to any fluid transport system in which a plurality of pumps are connected in series through conduits.

(Effects of the Invention) As is clear from the above description, according to the present invention, the flow rate of the upstream pump is controlled so as to force-feed the target original vehicle, and the flow rate of the upstream pump is controlled according to the discharge side pressure of the upstream pump and the flow rate of the pipe line. Since the pressure of the downstream pump is controlled to obtain an appropriate suction side pressure, cavitation on the suction side after the second pewter, which was caused by pressure loss on the piping, can be suppressed. The target flow rate can be stably pumped without damaging the pump.

Furthermore, compared to the case where a buffer tank is provided in the middle of the pipeline, the cost of the device including maintenance costs can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a system diagram showing the configuration of a conventional device. 1...Flow meter controller, 2...Rotation speed controller, 4, 5.
・・Water pump, 6・Flow detector, 7.8・Telemeter, 9・・Water feed valve, 10・Pipe line, 12.1
4...Pressure detector, 13...Calculator.

Claims (1)

[Claims] A pump control device for a fluid transfer system having a plurality of pumps connected in series through a pipe, including a flow rate detector for detecting the flow rate in the pipe, and configured to adjust the flow rate in the pipe to be equal to a set amount. a first control system that controls the upstream pump, and a first control system that detects the discharge side pressure of the upstream pump.
a pressure detector, a calculation means for calculating the suction side pressure of the adjacent downstream pump based on the detected values of the first pressure detector and the flow rate detector, and a suction side pressure of the downstream pump. and a second control system that controls the pump on the downstream side so that the suction side pressure is equal to the suction side pressure calculated by the calculation means. A pump control device featuring: